Is it possible to determine the number of elements of a c++ enum class?

Question

Is it possible to determine the cardinality of a c++ enum class:

enum class Example { A, B, C, D, E };

I tried to use si

Answer 1

If you make use of boost's preprocessor utilities, you can obtain the count using BOOST_PP_SEQ_SIZE(...).

For example, one could define the CREATE_ENUM macro as follows:

#include 

#define ENUM_PRIMITIVE_TYPE std::int32_t

#define CREATE_ENUM(EnumType, enumValSeq)                                  \
enum class EnumType : ENUM_PRIMITIVE_TYPE                                  \
{                                                                          \
   BOOST_PP_SEQ_ENUM(enumValSeq)                                           \
};                                                                         \
static constexpr ENUM_PRIMITIVE_TYPE EnumType##Count =                     \
                 BOOST_PP_SEQ_SIZE(enumValSeq);                            \
// END MACRO   

Then, calling the macro:

CREATE_ENUM(Example, (A)(B)(C)(D)(E));

would generate the following code:

enum class Example : std::int32_t 
{
   A, B, C, D, E 
};
static constexpr std::int32_t ExampleCount = 5;

This is only scratching the surface with regards to the boost preprocessor tools. For example, your macro could also define to/from string conversion utilities and ostream operators for your strongly typed enum.

More on boost preprocessor tools here: https://www.boost.org/doc/libs/1_70_0/libs/preprocessor/doc/AppendixA-AnIntroductiontoPreprocessorMetaprogramming.html

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As an aside, I happen to strongly agree with @FantasticMrFox that the additional Count enumerated value employed in the accepted answer will create compiler warning headaches galore if using a switch statement. I find the unhandled case compiler warning quite useful for safer code maintenance, so I wouldn't want to undermine it.